President Obama praised the designation of a new prime minister in Iraq on Monday, despite the protests of current office occupant Nouri al-Maliki.

"This is an important step towards forming a new government that can unite Iraq's different communities," Obama told reporters, calling for formation of a new Cabinet "as quickly as possible" and pledging U.S. support.

Al-Maliki called the naming of his successor illegal, and said the United States is standing "on the side of violating the constitution."

The political showdown comes less than a week after Obama authorized U.S. airstrikes to help battle fighters of the militant Islamic State in northern Iraq. In the days since, the president has repeatedly urged Iraqi lawmakers to form a new government as soon as possible.

Obama also said his "limited" military operations — designed to protect U.S. personnel and religious minorities under siege by militants — are making progress.

Echoing previous comments, Obama said "there is no American military solution to the larger crisis in Iraq," and the Iraqis must solve their own problems -- starting with formation of a government "that addresses the needs and grievances" of all the nation's people and religious factions.

Obama also said he spoke to the new prime minister-designate by phone.

For weeks, administration officials who have clashed with al-Maliki made little secret of their hopes for his departure, and they made their preference plain throughout the day on Monday,

Vice President Biden spoke by phone with the new prime minister-designate, al-Ibadi, as well as President Massoum, according to a pair of White House statements — neither of which mentioned al-Maliki.

"The prime minister-designate expressed his intent to move expeditiously to form a broad-based, inclusive government capable of countering the threat of the Islamic State of Iraq and the Levant (ISIL), and building a better future for Iraqis from all communities," said one of the statements.

Biden "relayed President Obama's congratulations and restated his commitment to fully support a new and inclusive Iraqi government, particularly in its fight against ISIL," it added.

Administration officials have made little secret of their hope that al-Maliki does not receive another term, though al-Maliki says he will fight for his job.

In other call, Biden commended Massoum "for meeting this key milestone and reiterated President Obama's repeated calls for the timely creation of a new, more inclusive government that will be able to address the legitimate concerns of all Iraqis," said the White House.

Biden also emphasized Obama's "desire to boost coordination with a new Iraqi government and Iraqi Security Forces to roll back gains by the Islamic State" in northern Iraq, the statement said.